FIG. 5 is a schematic diagram of an air pollution control apparatus of a coal combustion boiler. As shown in FIG. 5, combustion gas 11 generates steam in a generating tube within a furnace 12 of a coal combustion boiler 10 (the generated steam is separated into gas and liquid by a steam drum 13, the steam is guided into a super heater 14 and becomes overheated steam, the steam is used for driving a steam turbine, and then condensed water is circulated into a water tube in the furnace 12 and is again evaporated). The steam is overheated by the super heater 14 to heat water to be supplied to the coal combustion boiler 10 in an economizer 15, and then the steam is discharged from an exit of the economizer 15 as flue gas 16. The flue gas 16 from the economizer 15 is supplied to a denitrator 17, heats air 19 by heat exchange in an air heater 18, is supplied to a dust collector 20, is further supplied to a desulfurizer 21, and then is discharged to atmosphere as purge gas 22.
As the denitrator 17, one is proposed which sprays ammonium (NH3) to the flue gas 16 from the coal combustion boiler 10 upstream of the denitrator (catalyst unit), thereby reducing and denitrating the flue gas 16.
To reduce mercury included in flue gas, a system is proposed that sprays a chlorinating agent such as HCl upstream of the denitrator 17, oxidizes (chlorinates) the mercury on a catalyst, and reduces the mercury by a wet desulfurizer installed downstream (Patent Document 1).
Patent Document 1: Japanese Patent Application Laid-open No. H10-230137